“HENRI COANDA”
AIR FORCE ACADEMY
ROMANIA
“GENERAL M.R. STEFANIK”
ARMED FORCES ACADEMY
SLOVAK REPUBLIC
INTERNATIONAL CONFERENCE of SCIENTIFIC PAPER
AFASES 2015
Brasov, 28-30 May 2015
TRANSMISSION CODING SYSTEM USING HAMMING ENCODING
FHSS
Gabriel ANASTASIU*, Elena ANASTASIU**
*Faculty of Electrical Engineering and Computer Science, University of Suceava, Romania,
**“Alexandru cel Bun” College, Gura Humorului, Romania
Abstract: Current issues facing many communication systems, especially the unauthorized interception
requires solving by various methods against jamming type. These methods range from sub-level coding
and coding to mixed. In this article I present a mixed method that can be used in various transmission
systems.
Keywords: jamming, hamming, coding level.
1. INTRODUCTION
In current systems need the possibility of
transmission observed "hide" or encoding
information using different coding elements.
This signal encoding is required when
sending confidential data or maximum
security, such as a military system.
In this article I will try to present their own
contribution and that makes a double coding of
data, which provides a good security system to
intercept and a small cost. The system
presented below is an experiment conducted
on a small scale but can be extended to other
professional type systems using other modules
such as performing Intel Intel Edisson or
Galileo.
2. SYSTEM DESCRIPTION
The system is based on two elements
modular
development
board
Arduino
Leonardo [6] and Pololu Wixel radio [7].
Leonardo Arduino development board is
made by people from Arduino and is a board
based on ATMEGA32U4. It has 20 pin digital
input / output (of which 7 can be used as PWM
outputs and 12 analog inputs and a micro USB
connection. It also has 6 analog inputs /
outputs that can connect different sensors,
figure 1:
Figure 1. Arduino Leonardo parts.
Pololu Wixel transceiver type plate, Figure
2 [6] is a development board radio operating at
2.4 GHz frequency and allows multiple
applications among which one you will use
this material, i.e. FHSS (Frequency Hopping
Spread Spectrum). Implementation plate
modulation is done by programming the micro
USB port and then the communication
between Arduino board and Wixel.
Figure 2. Pololu Wixel Board.
Block diagram of the proposed system is
given in Figure 3:
Arduino Leonardo coding/deccodin
g Wixel Figure 3. Block diagram.
3. CODING SYSTEM
IMPLEMENTATION DECODE Hamming
FHSS
From the block diagram it can be seen that
the application source coding system is the
module Arduino Leonardo. Following tests
using NRZ coding or Hamming [1] revealed
that only encoding that provides secure is
indeed a model Hamming coding.
Hamming encoding is defined in the
literature as correcting code and error detector
and two errors.
The code contains four data bits d1, d2, d3,
d4 and 3 parity bits p1, p2, p3. Parity bits are
calculated as follows:
p1 sums d1, d2, d4
p2 sums d1, d3, d4
p3 sums d2, d3, d4
Organize bits in the code-word is:
p1 p2 d1 p3 d2 d3 d4
The encoding: code-word is determined by
calculating the corresponding parity using both
look how odd parity and parity.
The decoding: Calculated parity check with
the appropriate and correct actually sums and
correct parity and check showing 0.
An example of Hamming coding based on
which system you implement an algorithm for
Arduino Leonardo is:
The encoding enters the code-word 1001.
We calculate:
p1 = 1+0+1 = 0
p2 = 1+0+1 = 0
p3 = 0+0+1 = 1
resulting Hamming code 0 0 1 1 0 0 1 s are
represented by the underlined parity bits.
The decoding: 0011001. We assume that
you received without errors. We will
reconstruct the data bits: 1 0 0 1
Parity should be checked:
p1 + d1 + d2 + d4 = 0 + 1 + 0 + 1 = 0
p2 + d1 + d3 + d4 = 0 + 1 + 0 + 1 = 0
p3 + d2 + d3 + d4 = 1 + 0 + 0 + 1 = 0
How these values are 0 results that there
was error. We implemented an application that
supplied after running the Arduino
environment Arduino Sketch_apr17a [2], the
example shown above, the result provided
below:
this works for message of 4bits in size
enter message bit one by one: 1 2 3 4
the encoded bits are given below:
1 2 3 0 4199040 7 6 4201166 4
Code will be forwarded obtained board
transceiver type Pololu Wixel is scheduled to
work
FHSS
mode. Spread
Spectrum
modulation techniques such techniques are
defined as the bandwidth of the transmitted
signal is much larger than the bandwidth of the
original message, and the bandwidth of the
transmitted signal is determined by the
message to be transmitted and an additional
signal known as the spreading code. Spectrum
technology was first used during World War II
by the army, which has experienced extended
spectrum, low interference because it offered
much-needed security. Are two ways to
achieve spread: frequency hopping and direct
sequencing? Frequency hopping is one of the
variants of spread spectrum techniques that
allow the coexistence of multiple networks (or
other devices) in the same area. Frequency
hopping is resistant to attempts to decode
multiple
frequencies
by
multiplying
mechanism. Frequency
hopping
radio
transmission is a technique where the signal is
divided into several parts and then transmitted
through the ether using a random pattern of
jumping or "jump" frequencies. The frequency
hopping may be several times a second to a
few thousand times per second. Frequency
“HENRI COANDA”
AIR FORCE ACADEMY
ROMANIA
“GENERAL M.R. STEFANIK”
ARMED FORCES ACADEMY
SLOVAK REPUBLIC
INTERNATIONAL CONFERENCE of SCIENTIFIC PAPER
AFASES 2015
Brasov, 28-30 May 2015
hopping is the most easy to use spread
spectrum modulation model. Any radio with
digital control type frequency synthesizer can
theoretically be used in a radio system with
frequency hopping. This conversion requires
the addition of a generator pseudo noise (PN)
code to select frequencies for transmission or
reception. The best type FHSS systems using a
uniform frequency hopping band. FSS
subsystem produces an effect of spreading
pseudo random jump RF carrier frequency
over disponibile. The RF frequencies are
denoted f1 ... FN where N may represent
several radio harmonics made or more. An
illustration of a FHSS system type is given in
Figure 5:
4. EXPERIMENTAL RESULTS
To achieve a real implementation of a
software module to perform a FHSS Pololu
Wixel [7] we started from a dedicated
algorithm which comply with the elements of
Figure 5, Figure 6:
The implementation of this algorithm
translates as the workings of the FHSS Wixel
plate. So the result is a signal output which
theoretically cannot be decoded unless known
mathematical models applied, where it can be
seen mixing Hamming coded signal overbearing.
Figure 7. Wixel signal output.
If assume 1-bit error:
1. If 1 check bit bad:
Data is good, check bit itself got
corrupted.
Ignore check bits. Data is good.
2. If more than 1 check bit bad:
Data in error (single-bit error in
data). Which check bits are bad shows
you exactly where the data error was.
They point to a unique bit which is the
bit in error. In figure 9 is the FHSS
over Hamming function of time.
Data
Ove
Lost
Select
Trans
Resend
error
ack Figure 9. Wixel output signal.
change
report
ove
go to
next
increm
rx
Figure 6. Algorithm model FHSS WIXEL.
Implementation scheme is illustrated in
Figure 10 and can see two basic components
development board Arduino Leonardo Pololu
Wixel.
5. CONCLUSIONS &
ACKNOWLEDGEMENT
Figure 10. Schematics implementation.
Software implementation results in part
described in chapter three of this article are
measurable and can be highlighted and achieve
primary receiving system that logically plays
decoder. To achieve a simulation of the
transmission system described in the article we
used a number of lines of code containing
information that a wanted transmitted. View
information from the system I viewed it on the
Arduino Leonardo serial interface, results are
outlined in chapter 3, figure 11:
Applying this dual coding system can be very
useful because FHSS is highly resistant to both
the jamming systems, simply because the
algorithm to achieve the “frequency hopping”
allows "insurance" in front of potential
intruders but also because of coding Hamming
type that allows error correction.
This paper was supported by the project
"Sustainable performance in doctoral and postdoctoral research PERFORM - Contract no.
POSDRU/159/1.5/S/138963", project cofunded from European Social Fund through
Sectorial Operational Program Human
Resources 2007-2013.
REFERENCES
Figure 11.
Terminal.
Data
representation
Serial
The implementation of this algorithm and
combining with FHSS modulation coding type
Hamming we got a system that is difficult to
decode, at least theoretically but can be studied
and implemented other more advanced
systems such as Intel development board
Galileo or Intel Edison. Such a system can
provide a coding system to satisfy the
requirements of civil and military.
1. Micolau, J., Juvilla, O., "Hamming Block
Codes”, Raymond Hills, January (2000).
2. R.Petraru, and A.Velicu, “Basic practical
elements in the deployment of embedded
microprocessors using Arduino,” Ed.Techno
Media Sibiu, 2014 (references)
3. Robofun, Arduino for beginers
4. R.Santos, “Random Nerd Tutorials”
5. www.robofun.ro .
6. http://www.pololu.com .
7. http://www.arduino.cc .
8.http://www.ee.unb.ca/tervo/ee4253/Hammin
g.htm.